Input distribution in MadGraph

Hi,

It actually depends of what you want to do and which effects you want to include.

If you do not care about width effect and about spin-correlation, then
you can generate
> X > ...,
and then boost event by event your event according to your distribution
This is actually what madspin is doing in the "spinmode=none" mode.

We also have such type of mode for hepmc input (see the maddump paper).

Cheers,

Olivier

> On 22 Mar 2021, at 10:35, Maksym Ovchynnikov <email address hidden> wrote:
>
> New question #696182 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/696182
>
> Consider a particle X that decays into some SM particles. This part may be easily incorporated in MadGraph. Consider a case when X is produced in decays of some particle (say, B-meson) that are not incorporated (and may not be incorporated) in MadGraph. Let us assume however that we have a distribution of X from some side calculations.
>
> Is it possible to modify MadGraph in a way such that instead of generating events with X in MadGraph
>
> p p > X, X > ...
>
> we just generate
>
> X > ...,
>
> but provide the X spectrum as an input to MadGraph?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks Olivier! Does the mentioned syntax > X > ... assume that the X particle is at rest?

Also, I tried to run

generate > V > chi chi~

in MadGraph (V, chi, chi~ are new physics particles), but it said that "InvalidCmd : "> V > chi chi~" is a wrong process format. Please try again". What I made wrong there?

You have to do
generate V > chi chi~

Sorry the indentation of the email added a ">" that confuse you

Cheers,

Olivier

Hi again,

may I please ask you to clarify the following:

"This is actually what madspin is doing in the "spinmode=none" mode. We also have such type of mode for hepmc input (see the maddump paper)."

Does it mean that MadDump may use as an input a hepmc file with the spectrum and follow the procedure that you have described?

"If you do not care about width effect and about spin-correlation, then
you can generate
> X > ...,
and then boost event by event your event according to your distribution"

Yes,

Maddump can indeed take an hepmc as input and decay the pion/Kaon spectrum in that way.

Cheers,

Olivier